U.S. patent number 10,781,321 [Application Number 15/550,262] was granted by the patent office on 2020-09-22 for coating agent for oil seal.
This patent grant is currently assigned to NOK CORPORATION. The grantee listed for this patent is NOK Corporation. Invention is credited to Katsumi Abe, Natsumi Kimura.
United States Patent |
10,781,321 |
Kimura , et al. |
September 22, 2020 |
Coating agent for oil seal
Abstract
A coating agent for oil seal comprising 10 to 160 parts by
weight of a filler having a particle size of 0.5 to 30
.quadrature.m based on 100 parts by weight of isocyanate
group-containing 1,2-polybutadiene and being prepared as an organic
solvent solution, wherein a contact angle between a substrate
surface coated with the coating agent and engine oil is less than
35.degree.. The coating agent can improve wettability with oil and
reduce dynamic friction coefficient in oil, while increasing the
roughness of the coating surface. Thus, low torque characteristics
can be achieved, while maintaining excellent seal performance
inherent in oil seal.
Inventors: |
Kimura; Natsumi (Kanagawa,
JP), Abe; Katsumi (Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NOK Corporation |
Tokyo |
N/A |
JP |
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Assignee: |
NOK CORPORATION (Tokyo,
JP)
|
Family
ID: |
1000005068306 |
Appl.
No.: |
15/550,262 |
Filed: |
February 10, 2016 |
PCT
Filed: |
February 10, 2016 |
PCT No.: |
PCT/JP2016/053910 |
371(c)(1),(2),(4) Date: |
August 10, 2017 |
PCT
Pub. No.: |
WO2016/132982 |
PCT
Pub. Date: |
August 25, 2016 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20180030287 A1 |
Feb 1, 2018 |
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Foreign Application Priority Data
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|
|
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Feb 17, 2015 [JP] |
|
|
2015-028287 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D
7/40 (20180101); C09D 7/65 (20180101); C09D
7/68 (20180101); C09D 7/61 (20180101); F16J
15/3204 (20130101); F16J 15/3284 (20130101); C09D
7/69 (20180101); C09D 109/00 (20130101); C09D
153/00 (20130101); F16J 15/32 (20130101); C08L
27/00 (20130101); C08L 27/18 (20130101); C08L
69/00 (20130101); C08L 83/04 (20130101); C08K
3/36 (20130101) |
Current International
Class: |
C09D
7/40 (20180101); C09D 7/65 (20180101); C09D
109/00 (20060101); C09D 153/00 (20060101); F16J
15/3204 (20160101); F16J 15/3284 (20160101); C09D
7/61 (20180101); C08K 3/36 (20060101); C08L
83/04 (20060101); C08L 69/00 (20060101); C08L
27/18 (20060101); C08L 27/00 (20060101); F16J
15/32 (20160101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
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2003-213122 |
|
Jul 2003 |
|
JP |
|
3893985 |
|
Dec 2006 |
|
JP |
|
2007332269 |
|
Dec 2007 |
|
JP |
|
2008-189892 |
|
Aug 2008 |
|
JP |
|
2006-292160 |
|
Dec 2011 |
|
JP |
|
4873120 |
|
Dec 2011 |
|
JP |
|
WO 2016/047640 |
|
Mar 2016 |
|
WO |
|
WO 2016/047641 |
|
Mar 2016 |
|
WO |
|
Other References
Tora, Toshihiro et al., JP-2007332269-A, Dec. 27, 2007 (Machine
translation) (Year: 2007). cited by examiner .
International Search Report from corresponding PCT application No.
PCT/JP2016/053910 dated May 17, 2016 (4 pgs). cited by applicant
.
International Preliminary Report on Patentability and Written
Opinion from corresponding PCT application No. PCT/JP2016/053910
dated Aug. 22, 2017 (8 pgs). cited by applicant.
|
Primary Examiner: Huang; Cheng Yuan
Claims
The invention claimed is:
1. An organic solvent solution based coating agent for oil seal
comprising 10 to 160 parts by weight of a filler having a particle
size of 0.5 to 30 .mu.m based on 100 parts by weight of isocyanate
group-containing 1,2-polybutadiene, wherein the organic solvent
solution based coating agent provides a contact angle between a
substrate surface coated with the coating agent and engine oil of
less than 35.degree., wherein the filler is silica, silicone resin
or polycarbonate.
2. An oil seal coated with the coating agent according to claim 1.
Description
RELATED APPLICATION
This application is a 35 U.S.C. .sctn. 371 national phase filing of
International Patent Application No. PCT/JP2016/053910, filed Feb.
10, 2016, which claims priority under 35 U.S.C. .sctn. 119 to
Japanese Patent Application No. 2015-028287, filed Feb. 17, 2015,
the entire disclosure of which is hereby expressly incorporated by
reference.
TECHNICAL FIELD
The present invention relates to a coating agent for oil seal. More
particularly, the present invention relates to a coating agent for
oil seal capable of reducing friction in oil.
BACKGROUND ART
Oil seal is widely used as an important machine element in the
field of vehicles, industrial machines, and the like. Oil seal is
used for the purpose of movement and sliding; however, in that
case, deterioration of the seal oil and the sealing material due to
the frictional heat of the seal, and energy loss in devices due to
frictional resistance are often problematic.
In order to reduce the torque of the oil seal, it is preferable
that oil is held on the sliding surface. For this purpose, it is
required to improve wettability with oil, while increasing the
roughness of the sliding surface. However, in the case of a coating
agent comprising, as a filler, fluororesin particles having a low
particle size of 0.1 to 10 .mu.m, which were conventionally used in
coating agents, the surface energy of fluororesin was high, so that
it was difficult to significantly improve wettability with oil.
Further, because of the small particle size, it was also difficult
to increase the roughness of the coating surface.
Meanwhile, the friction of oil seal can be reduced by forming a
coating film of a material having a frictional coefficient lower
than that of the sealing material on the sliding surface of the oil
seal lip part; however, if the coating film is removed during
sliding, the effect of reducing friction is lost.
The present applicant has previously proposed, in Patent Documents
1 and 2, surface-treating agents for vulcanized rubber comprising
10 to 160 parts by weight respectively of wax having a softening
point of 40 to 160.degree. C. and fluororesin, or 10 to 160 parts
by weight respectively of fluororesin and polyethylene resin, based
on 100 parts by weight of isocyanate group-containing
1,2-polybutadiene, wherein the surface-treating agents are prepared
as organic solvent solutions. These surface-treating agents are
supposed to be effectively applicable to oil seal, and the like;
however, further lower torque characteristics have recently been
demanded.
PRIOR ART DOCUMENTS
Patent Documents
Patent Document 1: JP-B-3893985
Patent Document 2: JP-B-4873120
OUTLINE OF THE INVENTION
Problem to be Solved by the Invention
An object of the present invention is to provide a coating agent
that can achieve low torque characteristics, while maintaining
excellent seal performance inherent in oil seal.
Means for Solving the Problem
The above object of the present invention can be achieved by a
coating agent for oil seal comprising 10 to 160 parts by weight of
a filler having a particle size of 0.5 to 30 .mu.m based on 100
parts by weight of isocyanate group-containing 1,2-polybutadiene
and being prepared as an organic solvent solution, wherein a
contact angle between a substrate surface coated with the coating
agent and engine oil is less than 35.degree..
Effect of the Invention
As the filler contained in the coating agent, a filler that has a
large particle size and that results in a contact angle of less
than 35.degree. between a substrate surface coated with the coating
agent and engine oil is selected to thereby can improve wettability
with oil and reduce dynamic friction coefficient in oil, while
increasing the roughness of the coating surface. Thus, the
excellent effect of achieving low torque characteristics can be
exhibited.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
As the isocyanate group-containing 1,2-polybutadiene, one having a
molecular weight of about 1,000 to 3,000 in which an isocyanate
group is added as a terminal group is used. This can be a
commercial product, for example, Nisso TP-1001 produced by Nippon
Soda Co., Ltd. (solution containing 50 wt. % of butyl acetate) can
be used as it is. Because an isocyanate group is added as a
terminal group, reaction with the functional group on the surface
of vulcanized rubber and the hydroxyl group-containing component
occurs to cause bonding and curing. The affinity and compatibility
with rubber of the polybutadiene resin are superior to those of
polyurethane resin that similarly react with an isocyanate group to
achieve a higher molecular weight. Thus, the polybutadiene resin is
characterized by excellent adhesion with rubber, particularly
excellent friction and abrasion resistance characteristics.
Usable fillers are those that have a particle size of about 0.5 to
30 .mu.m, preferably about 1.0 to 30 .mu.m, that are eventually
prepared as coating agents, and that result in, after coating of an
oil seal surface, a contact angle of less than 35.degree. or less
between the coated substrate surface and engine oil (e.g., Engine
Oil OW-20). Examples thereof include particles of fluororesin,
silica, silicone resin, polycarbonate, urethane resin, acrylic
resin, carbon black, or the like. If the particle size of the
filler is smaller than the above range, the roughness of the
coating surface is smaller, the effect of holding oil cannot be
maintained, and the torque of the seal sliding surface is higher.
In contrast, if the particle size of the filler is greater than the
above range, the roughness of the coating surface is greater, and
sealing properties are deteriorated to cause the leakage of oil. In
addition, if a filler that results in a contact angle after coating
greater than the above range is used, oil is repelled, the oil
holding force of the oil seal sliding surface is impaired, and it
is difficult to achieve desired low torque characteristics.
Examples of fluororesin include polytetrafluoroethylene [PTFE],
tetrafluoroethylene/hexafluoropropylene copolymers,
tetrafluoroethylene/perfluoro-alkyl vinyl ether) copolymers,
polyvinylidene fluoride, polyvinyl fluoride,
ethylene/tetrafluoroethylene copolymers, and the like. Usable
examples of such fluororesin particles include particles prepared
by classifying a fluororesin obtained by block polymerization,
suspension polymerization, solution polymerization, emulsion
polymerization, or the like to a particle size of about 0.5 to 30
.mu.m; particles prepared by finely dispersing a dispersion
obtained by suspension polymerization, solution polymerization,
emulsion polymerization, or the like, by shear stirring, etc., to a
particle size of about 0.5 to 30 .mu.m; or particles prepared by
coagulating and drying a product obtained by polymerization
mentioned above, followed by atomization to a particle size of
about 30 .mu.m or less by dry pulverization or cooling
pulverization.
Moreover, examples of silica include amorphous silica, such as
dry-process silica produced by, for example, thermal decomposition
of halogenated silicate or an organosilicon compound, or heat
reduction of silica sand, followed by air oxidation of vaporized
SiO; and wet-process silica produced by, for example, thermal
decomposition of sodium silicate. Examples of the silicone resin
include condensation reaction type silicone resin, addition
reaction type silicone resin, and ultraviolet or electron beam
curable silicone resin. Examples of polycarbonate include aromatic
polycarbonate, aliphatic polycarbonate, aliphatic-aromatic
polycarbonate, and the like. In the present invention, these are
not particularly limited as long as the particle size is about 0.5
to 30 .mu.m. Commercial products thereof can be used as they
are.
The filler is used at a rate of about 10 to 160 parts by weight,
preferably about 25 to 120 parts by weight, based on 100 parts by
weight of the isocyanate group-containing 1,2-polybutadiene. If the
ratio of the filler is greater than this range, adhesion with
rubber and friction abrasion resistance characteristics are
deteriorated, the flexibility of the coating is impaired, and
cracks are formed on the coating film after curing. In contrast, if
the ratio of the filler is less than this range, sliding properties
and non-adhesiveness are deteriorated, and the frictional
coefficient of the coating surface increases.
The isocyanate group-containing 1,2-polybutadiene and the filler
are prepared as a solution (dispersion) of an organic solvent,
which is used as a coating agent for oil seal. Examples of the
organic solvent include toluene, xylene, ethyl acetate, butyl
acetate, methyl ethyl ketone, methyl isobutyl ketone, and the like.
For such organic solvents, ones that are commercially available in
general may be used as they are. The amount of dilution with an
organic solvent is suitably selected depending on the coating
thickness and the coating method. The film thickness is generally
about 1 to 30 .mu.m, preferably about 3 to 20 .mu.m. If the film
thickness is less than this range, the entire rubber surface cannot
be coated, and sliding properties and non-adhesiveness may be
impaired. In contrast, if the film thickness is greater than this
range, the stiffness of the coating surface becomes higher, and
sealing properties and flexibility may be impaired. The film
thickness is preferably about 3 to 20 .mu.m for use application
such as seal parts.
Examples of the rubber for oil seal that can be treated with such a
coating agent include general rubber materials such as
fluororubber, nitrile rubber, hydrogenated nitrile rubber,
ethylene-propylene rubber, styrene-butadiene rubber, acrylic
rubber, chloroprene rubber, butyl rubber, and natural rubber. Among
them, rubber materials having little blooming of a rubber
compounding agent such as an antioxidant and oil, which are
compounded in the rubber, to the rubber surface layer are
preferably used. The compounding proportion of each component, the
type of organic solvent, the amount of organic solvent, and the
organic solvent mixing ratio are suitably selected depending on the
rubber material and the purpose.
Examples of the coating method of the coating agent to an oil seal
surface include, but are not limited thereto, dipping, spraying,
roll coater, flow coater, and the like. In this case, it is
preferable that dirt, and the like, on the rubber surface are
previously removed by washing or the like before the coating agent
is applied. In particular, washing with water, a detergent, a
solvent, etc., and drying are performed when materials bloomed and
bled from the rubber are deposited on its surface.
After the coating agent is applied to the oil seal surface, heat
treatment is performed at about 150 to 250.degree. C. for about 10
minutes to 24 hours. If the heating temperature is lower than this
range or the heating time is shorter than this range, the curing of
the film and the adhesion with the rubber are insufficient, and
non-adhesiveness and sliding properties are deteriorated. In
contrast, if the heating temperature is higher than this range or
the heating time is longer than this range, heat aging of the
rubber occurs. Therefore, it is necessary to suitably set the
heating temperature and heating time depending on the heat
resistance of various rubbers.
Moreover, for item for which a reduction in the amount of
outgassing is required, heat treatment, reduced pressure treatment,
extraction treatment, etc., can be performed singly or in
combination; however, heat treatment is economically the best. In
order to reduce the amount of outgassing, heat treatment at about
150 to 250.degree. C. for about 1 to 24 hours is preferable. In
order to gasify low-molecular components in the rubber and
low-molecular components contained in polybutadiene in the film,
the higher the temperature and the longer the time, the more
effective.
EXAMPLES
The following describes the present invention with reference to
Examples.
Example 1
TABLE-US-00001 Isocyanate group-containing 1,2-polybutadiene 200
parts by weight (TP1001, produced by Nippon Soda Co., Ltd.; (100
parts by weight) containing 50% of butyl acetate) Silica (Silica
6B, produced by Chuo Silica Co., 43 parts by weight Ltd.; particle
size: 7 .mu.m) Butyl acetate 1798 parts by weight
The above components were mixed, and a coating agent solution
comprising this butyl acetate solution was spray coated to
vulcanized rubber (thickness: 2 mm) to a thickness of 10 to 30
.mu.m, followed by heat treatment at 200.degree. C. for 10 hours.
Then, the contact angle and the dynamic friction coefficient in oil
were measured. Each of the part by weight is represented by a part
by weight of the solution, and the actual part by weight of each
component is shown in parentheses (the same applies to the
following Examples and Comparative Examples).
Contact angle: Using Drop Master 500 (produced by Kyowa Interface
Science Co., Ltd.), the contact angle to Engine Oil OW-20 was
measured
A contact angle of less than 35.degree. was evaluated as 0, and
that of 35.degree. or more was evaluated as x
Dynamic friction coefficient in oil: Using a surface property
tester (HEIDON TYPE14DR, produced by Shinto Scientific Co., Ltd.),
reciprocation was carried out under the following conditions, and
the dynamic friction coefficient on the forward side was measured.
A dynamic friction coefficient of less than 0.2 was evaluated as 0,
and that of 0.2 or more was evaluated as x Load: 50 g Rate: 50
mm/min Reciprocation distance: 50 mm Indenter: a steel ball having
a diameter of 10 mm Oil type: Engine Oil OW-20
Note: The dynamic friction coefficient in oil is an evaluation
correlated with the real system evaluation of oil seal. When the
dynamic friction coefficient in oil using the above test piece is
low, the real system evaluation using oil seal is supposed to be
excellent.
Example 2
In Example 1, 614 parts by weight (43 parts by weight as
polycarbonate) of polycarbonate (Polycarbonate TR-7; produced by
Gifu Shellac Manufacturing Co., Ltd.; particle size: 6 .mu.m;
containing 93% of toluene) was used in place of silica.
Example 3
In Example 1, the same amount (43 parts by weight) of silicone
resin particles (Tospearl 130, produced by Momentive Performance
Materials Inc.; particle size: 3 .mu.m) was used in place of
silica.
Example 4
In Example 1, the same amount (43 parts by weight) of silicone
resin particles (X-52-703, produced by Shin-Etsu Chemical Co.,
Ltd.; particle size: 0.8 .mu.m) was used in place of silica.
Comparative Example 1
In Example 1, the same amount (43 parts by weight) of silicone
resin particles (Nylon SP-10, produced by Toray Co., Ltd.; particle
size: 10 .mu.m) was used in place of silica.
Comparative Example 2
In Example 1, the same amount (43 parts by weight) of silicone
rubber particles (TORAYFIL E606, produced by Toray Co., Ltd.;
particle size: 2 .mu.m) was used in place of silica.
Comparative Example 3
In Example 1, the same amount (43 parts by weight) of PTFE (Fluon
172J, produced by AGC Seimi Chemical Co., Ltd.; particle size: 0.2
.mu.m) was used in place of silica.
Reference Example
In Example 1, the coating agent solution was replaced with a
coating agent solution comprising 50 parts by weight of
polybutadiene, 1567 parts by weight of a PTFE solution (solid
matters content: 5%; 78.35 parts by weight), and 1567 parts by
weight of a polyethylene wax solution (solid matters content: 5%;
78.35 parts by weight), which corresponds to the invention
disclosed in Patent Document 1.
The results obtained in the foregoing Examples, Comparative
Examples, and Reference Example are shown in the following
Table.
TABLE-US-00002 TABLE Measure- ment Comparative evaluation Example
Example Reference item 1 2 3 4 1 2 3 Example Contact 10.8 8.7 22.7
30.5 42.1 38.2 38.1 39.7 angle .largecircle. .largecircle.
.largecircle. .largecircle. X X X X Dynamic 0.15 0.15 0.18 0.19
0.27 0.26 0.25 0.28 friction .largecircle. .largecircle.
.largecircle. .largecircle. X X X X coefficient in oil
INDUSTRIAL APPLICABILITY
The coating agent of the present invention achieves low torque
characteristics, while maintaining excellent seal performance
inherent in oil seal; therefore, the coating agent of the present
invention can be effectively used not only for oil seal, but also
for prevention of adhesion, reduction of friction, prevention of
abrasion, etc., of rubber parts, such as rubber rolls for copiers,
rubber belts for copiers, industrial rubber hoses, industrial
rubber belts, wipers, automobile weather strips, glass runs, and
the like.
* * * * *